Expectorant and antitussives brief introduction

Cough, Pharyngeal demulcent,Expectorant, Antitussives

1. Expectorants & Antitussives Prepared by: Kakade Samrudhi &Throat Pragati Guided by: Asst. Prof. Sidwadkar.I.H (Pharmacology Department) SCHOOL OF PHARMACY & RESEARCH CENTER BARAMTI

2. Expectorants and antitussives are those drugs that are used to treat cough. Cough : it is a protective reflux , it’s purpose being expulsion of respiratory secretions and forging particles from air passages. Pharyngeal demulcent : pharyngeal demulcent soothe the throat and reduce afferent impulses from the inflamed pharyngeal mucosa , thus provide symptomatic relief in dry cough arising from throat. Expectorants : they are also known as mucokinetics. These are those drugs which believed to increase bronchial secretions or reduce it’s viscosity, facilitating its removal by coughing. Antitussives : these are drugs that act in the CNS to raise the threshold of cough centre or act peripherally in respiratory tract or reduce tussal impulses, or both these actions.

3. CLASSIFICATION

4. Mechanism of Action I. Pharyngeal Demulcent: Soothe the throat Reduce afferent impulse from inflamed / irritated pharyngeal mucosa. II. Expectorants: There are two types of mechanisms Secretion enhancers Mucolytics

5. a) Secretion enhancer Expectorants Increases bronchial secreation or decreases viscosity of cough Easy removal of cough E.g. 1.Sodium/ potassium citrate: Increases bronchial secreation or Reduce viscosity by salt action 2.Potassium iodide: secreted by bronchial glands can irritate airways mucosa prolong use cause iodism 3.Guaiphenesin, vasaka, tolu balsam: plant products enhance bronchial secreation by tracheobronchial glands 4.Ammonium salts: increases bronchial secreation

6. b) Mucolytics: These agents dissolve thick mucous Helps to relieve respiratory difficulties By breaking disulfide bonds in mucopolysaccharides Decreases the viscosity of secretions Easy expulsion of mucous

7. Examples of mucolytics: Uses of mucolytics: Tracheostomy Asthmatic bronchitis Cystic fibrosis Example Mechanism of action 1. Bromhexine Derivative of alkaloid vasicine(obtained from vasaka). Depolymerization of mucopolysaccharide and makes mucous less viscous 2. Ambroxol metabolite of bromhexine and gives same action as bromhexine. 3.Acetylcysteine and carbocysteine opens disulphide bonds in the mucoproteins present in sputum and makes it less viscid.

8. III. Antitussives: They act by two mechanism Antitussives cns Peripherally To raise the threshold of cough centre To reduce tussal impulse

9. Examples of antitussives: 1. Opioids: 2. Non opioids: Example Mechanism of action a) codeine Opium alkaloid , less potent than morphine and suppress cough for about 6 hrs. Contraindicated in asthma b) Ethylmorphine Closely related to codeine which is methylmorphine Respiratory depressant properties c)Pholcodine Longer acting upto 12 hrs. Example Mechanism of action a) Noscapine Depresses cough but has no narcotic, analgesic or dependence inducing properties b) Dextromethorphan Synthetic central NMDA (N- methyl d-aspartate) receptor antagonist .It is d- isomer has antitussive action and l- isomer has analgesic action

10. 3. Antihistaminics: It is a sedative and have anticholinergic action. They have lack selectivity for cough centre. Examples of antihistaminics Example Mechanism of action a) Chloramphenicol Bind to H 1 receptor & block action of endogenous histamine b) Diphenhydramine Block action of H 1 receptor c) Promethazine H 1 receptor antagonist; blocks the action of histamine

11. iv. Bronchodilators : They can induce bronchospasm or aggravate the cough. Examples of bronchodilators: 1. Salbutamol Activates β 2 receptor in bronchial smooth muscle Activates adenyl cyclase activity increases cAMP Smooth muscle relaxation Bronchodilation. 2. Terbutaline Releases bronchial smooth muscle By stimulating β 2 adrenergic receptor Inhibits release of hypersensitivity mediators Specially from mast cells.